用繩子打結是大家都會的事情,，還可以玩出各種花樣,，但是用微小的分子鏈條來打結可不是一件容易的事,。英國研究人員最近在分子尺度上打出了迄今最復雜的人工紐結，這是一個漂亮的“五葉結”,。
英國愛丁堡大學等機構的研究人員在新一期《自然—化學》雜志上報告說,，他們用一些經(jīng)過變化的醛類和胺類分子組成的鏈條，生成了一個與5片花瓣的梅花相似的結構,，這種結構被稱為“五葉結”,。這是迄今人工完成的最復雜的“分子結”，以前研究人員只在分子尺度上打出過像三個環(huán)套在一起那樣的“三葉結”,。
值得一提的是,，本次研究中用來打結的“繩子”，也就是由分子組成的鏈條,，只有160個原子長,，長度為16納米（1納米為百萬分之一毫米），而粗細程度只有頭發(fā)絲的8萬分之一,。這樣的“繩子”難以手工編織,，是通過化學反應讓它們自發(fā)形成“五葉結”的,。
分子結構上的紐結對于科研有重要意義,，比如說橡膠的彈性就大部分來源于其分子結構的紐結和糾纏，通過研究分子紐結,，有助于更好地理解相關物質的特性,，還有助研發(fā)新型材料。(生物谷 Bioon.com)
doi:10.1038/nchem.1193
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A synthetic molecular pentafoil knot
Jean-François Ayme,1 Jonathon E. Beves,1 David A. Leigh,1 Roy T. McBurney,1 Kari Rissanen2 & David Schultz1
Knots are being discovered with increasing frequency in both biological and synthetic macromolecules and have been fundamental topological targets for chemical synthesis for the past two decades. Here, we report on the synthesis of the most complex non-DNA molecular knot prepared to date: the self-assembly of five bis-aldehyde and five bis-amine building blocks about five metal cations and one chloride anion to form a 160-atom-loop molecular pentafoil knot (five crossing points). The structure and topology of the knot is established by NMR spectroscopy, mass spectrometry and X-ray crystallography, revealing a symmetrical closed-loop double helicate with the chloride anion held at the centre of the pentafoil knot by ten CH···Cl– hydrogen bonds. The one-pot self-assembly reaction features an exceptional number of different design elements—some well precedented and others less well known within the context of directing the formation of (supra)molecular species. We anticipate that the strategies and tactics used here can be applied to the rational synthesis of other higher-order interlocked molecular architectures.
